Method and apparatus for the automatic stuffing of meat products into a double casing comprising a sheet and a net

ABSTRACT

Based on a conventional installation including a stuffing-portioning machine ( 1 ) and a fast clipper ( 2 ), duly synchronised, between which is established a shaping device ( 3 ) that converts the film ( 5 ) meant to wrap food products that is supplied in the form of a coil into a tubular element that can be coupled to the stuffing tube ( 3 ), on which is coaxially mounted a second tube ( 8 ) bearing an external casing ( 9 ) based on a tubular net, the invention consists of using tubes ( 4 ) and ( 8 ) with a small diameter, much smaller than that of the finished product, so that the film ( 5 ) is adapted to the tube ( 4 ) after the former is profusely folded longitudinally, while the small diameter of the tube ( 8 ) allows the multilayer shirring of the tubular net ( 9 ), using the pressure provided by the pumping system of the stuffing machine ( 1 ) to achieve the radial expansion of the film ( 5 ) and the tubular net ( 9 ) to obtain the final diameter of the finished product, which will vary according to the speed with which it is separated from the double clipper ( 2 ) carried by a conveyor belt ( 12 ) with an adjustable speed.

OBJECT OF THE INVENTION

The present invention relates to an automatic method for fully packagingmeat products in a dual casing, which internally consists of any type ofedible or inedible film and externally consists of an elastic tubularnet, and also relates to the device for executing said method.

The present invention consists of a method for stuffing in a double filmand net casing in which the meat product is passed through a tube with asmall diameter, independent of the size of the finished product andconsiderably smaller than it. The inner part of the double casingconsists of the film, which has overlapping edges and forms a cylinderaround the tube with a small diameter, adapting itself to the latter bylongitudinal folds. The net tube constituting the outer part of thedouble casing also has a small diameter, which has two effects: on onehand, the full automation of the system to increase its speedconsiderably as it allows using a conventional stuffing-proportioningmachine coupled to a double clipper, fast and conventional as well asduly synchronised with the first machine; and on the other hand, agreater loading capacity of the tubular net, with the resulting increasein system autonomy, while feeding the film continuously from a coil.

The diameter of the final product is obtained from the pressurecommunicating the stuffing machine pumping system and as a function ofthe speed with which the stuffed product moves away from the stuffingdevice.

BACKGROUND OF THE INVENTION

The present invention mainly corresponds to the field of food productpackaging, more specifically to the meat product industry. There are agreat variety of products wrapped in film for processing, handlingand/or conservation. The use of a film is often complemented with atubular net and finds a specific application in special products inwhich the appearance of the product is important.

The film and net assembly form a casing in which the main purpose of thefilm is to contain liquid parts, prevent excessive evaporation duringthe heat process, allow smoking, provide shine, colour and appearance tothe product surface, facilitate elimination of the net and of the filmitself if it is not edible, and must also be soft enough to allow thenet to transmit its imprint on the product, giving it a characteristicappearance. The use of the film and net also allows using chopped meatand meat parts of various sizes and qualities, even meat emulsions andfine pastes, alone or mixed with the former in various proportions, asthe film and net assembly confines and holds inside it the stuffedproduct until it coagulates and binds in the heat process, therebyallowing the manufacture of reconstituted meat products.

Films and tubular nets are currently applied in the food industrymanually and mechanically. For this purpose, the films are supplied incut sheets or in coils of greater or lesser length, ranging from 5 to250 meters. Nets are supplied as rolls with minimum lengths of about 50meters. A manual form of application consists of wrapping the foodproduct with the films and covering it with the net, making it passthrough the inside of a hollow metal cylinder or tube that supports agiven amount of tubular net axially shirred or compressed on it,obtaining on the opposite end of the cylinder the product with the netthat in this manner will cover it. This procedure is described in U.S.Pat. No. 4,621,482 (Crevasse, Gammon, Sullivan 1986). An even simplerprocedure is described in U.S. Pat. No. 4,719,116 (Crevasse 1988).

The mechanical process is performed by “applicators”, which wrap theproduct simultaneously with the film and net. A typical applicatorcomprises a film-coil bearing roller, a device for conforming a cylinderwith the film and a tube running inside the film tube formed throughwhich the food product is made to pass. A tube is placed concentricallyto this assembly in which a given quantity of net has been compressed.The end of the tube formed by the film and the end of the compressed netportion are taken jointly in front of the open end of the stuffing tubeand jointly closed with a clip, knot or any suitable system, so that thesystem is left ready to be stuffed wither by mechanical pumping or by amanually or pneumatically actuated piston. When the product is pushedout of the tube it simultaneously pulls the film and tubular net,thereby being wrapped by both. This procedure and the device forperforming it are respectively described in the U.S. Pat. No. 4,910,034(Winkler 1990) and U.S. Pat. No. 4,958,477 (Winkler 1990). Devices forcompressing the nets are also described in U.S. Pat. No. 5,273,481(Sullivan 1993) and U.S. Pat. No. 4,924,552 (Sullivan 1990).

The full meat product packaging procedure in which the describedapplicators participate is comprised of the following operations:

-   -   Feeding the meat.    -   Pushing the meat through the tube.    -   Holding and shaping the piece being stuffed.    -   Cutting the casing.    -   Clipping or stapling the ends.    -   Extracting the stuffed piece.    -   Piercing the casing to eliminate air bubbles.

These operations are in general performed in three different mannersaccording to the type of applicator, stapling or clipping machine usedand the extent of mechanisation required. The systems used are:

-   -   Systems with manual feeding and clipping.    -   Systems with automatic feeding and manual clipping.    -   Systems with automatic feeding and clipping.

The first system is the least mechanised of the three and uses a pistonapplicator. After the product is stuffed it is manually collected by theother end of the tube, which is coated in the double casing, while it ispulled to thus provide he required amount of double casing. After theentire product has left the tube and it is fully covered in the doublecasing, the latter is held by its rear part and cut. After it is cut thepiece is shaped by pressing the meat in the casing until it has therequired tension and the two ends are clipped or stapled in a simplemanual clipper normally located nearby. The operation is completed withthe manual piercing of the film surface to eliminate air trapped duringthe stuffing and placing the stuffed pieces in the cart where they willbe cooked. This system is the slowest of all and requires the highestmanpower. One person is needed to feed the meat, another to hold andshape it and a third to clip and pierce it. The production rate istherefore generally less than 4 pieces per minute.

The second system uses a mechanical pumping applicator. The meat tube iscoupled on its rear by a suitable connection system to a stuffingmachine that pumps a programmed amount of meat product each time. Thisprocedure has obvious advantages over the previous one. The first one isthat uniform amounts of meat are impelled each time, the operator onlyhaving to press a button or step on a pedal, and that the amount of airtrapped in the stuffed product is less, as the meat tube is always fullof meat and it can only be accessed through the space between the meattube and the net tube, this is, through the space in which the filmruns. The subsequent operations of holding and shaping the pieces,cutting, clipping or stapling the ends and piercing the pieces are asdescribed for the previous case, with the only added difficulty that asthe tube remains full of meat the operator must manually strangle thestuffed piece at the end of the stuffing tube, separating the meat massand pulling on the double casing until enough of it is exposed to cutand/or clip it, according to the method employed. The rate of thissystem is somewhat higher, around 5 parts per minute, and the operationcan be performed by only 2 persons, one to hold, shape and cut the pieceand the other to clip and pierce it.

The third system automates the feeding, pushing, shaping, clipping andcutting operations of the pieces, but not their piercing to eliminatethe air. Although in the previous systems the applicators may be usedwith several types of stuffers and/or clippers, in this case the systemconstitutes an assembly integrated in a single machine that includesportioning, pushing, separation and clipping. The product is fed by anapplicator coupled to a stuffing machine, with the difference that theimpulsion piston is pneumatically actuated. At the outlet of the meatstuffing tube is placed the holding, shaping, cutting and clippingmechanism, which consists of a system with two pairs of double clamps,in between which is the stapler. The sequence of operations is asfollows: after the meat piece has been placed inside the stuffing tube,the first pair of clamps placed immediately after the end of thestuffing tube opens to allow the latter to pass between them and throughthe clipper until it reaches the second pair of clamps, which are open,but not surpassing them so that the second pair can close without beinghindered by the tube. The end of the tube is already closed by he doublecasing held by a clip. Then the piston that pushes out the meat from thetube covered by the double casing is triggered. When the piston recedesthe second pair of clamps closes, strangling and holding the doublecasing immediately after the stuffed meat mass. At this time he tuberecedes to its initial position, thereby releasing an amount of doublecasing with a length equivalent to this recession movement, the firstpair of clamps closing to hold and collect the double casing at itsheight so that the stapling machine can place a pair of staples in thearea included between the double clamps, simultaneously cutting thedouble casing between them. The piece formed in this manner resting onan inclined path of freely turning rollers falls under gravity, exitingthe machine, where an operator pierces it and places it on the cartwhere it will be cooked. The advance of the tube between the clampsbefore the meat is pushed is necessary to prevent the product fromcolliding against these when it is stuffed and to allow the second pairto strangle the double casing, enclosing all the stuffed meat. Thisrequires sizing the system in correspondence with the meat tubediameter. This system is the fastest of the three and can reach a rateof 6 to 7 pieces per minute, with an operator collecting and piercingthe pieces, assisted part of the time by another that loads the net. Thesecond operator normally attends to two machines, so that one can saythat each machine requires 1.5 operators. This system saves doublecasing due to the automatic product shaping carried out by the clamps,as the piece tail ends are short and constant, their length beingdetermined by the distance between the two pairs of clamps, which isconstant. Although this system automates all stuffing operations, theirrate cannot exceed 7 parts per minute as the sequence of operationsdescribed is very slow. This slowness is due to the size and weight ofthe moving parts, clamps, advancing and receding tube, piston, clippingmachine, etc. and to its pneumatic actuation. Additionally, the machineis expensive and specific to this type of products.

Regardless of the system used, it is common to add to all theaforementioned operations the passage of the finished parts through avacuum chamber as a complement to piercing, to help eliminate the airtrapped during the stuffing, which causes important problems affectingthe external appearance of the finished product and resulting insignificant financial losses. This operation requires an additionaloperator.

In all of the above cases the diameter of the tubes through which themeat is passed is similar to that of the final product after it isclosed, clipped or stapled. This implies that the cylinder formed by thefilm around the meat tube has a diameter similar to that of the finalproduct and that the elastic net shirred on the outer tube is extendedto the degree that it will be in the final product. The reason for thisis that in this way the pouch or bag shaped assembly formed by the filmand the net is open at its maximum extension and offers a lowerresistance to be filled with the meat. This procedure is not lackingweak points that could be improved:

The systems hitherto developed have not attained a full and efficientautomation for processing products stuffed in a double film and netcasing. Machines have been developed, such as that previously describedin the third system, both for stuffing entire muscles or large pieces ofmeat and for reconstituted products that also staple or clip the piecesautomatically, but these machines are specific for this operation, aswell as slow, large and costly, as they are designed to perform theseparation and clipping operations of stuffed pieces through tubes whosediameter is similar to that of the finished piece. This means that it isnecessary to perform the slow sequence of operations previouslydescribed, which requires a specific complex machine, large and costly.The system solves some of the drawbacks inherent to this type ofelaboration, but the operation continues to be slow, not above sevenpieces per minute, and the stuffed products include a great amount ofsurface air that is difficult and never completely eliminated.

In addition, this system does not allow a continuous stuffing that keepsthe tube full of meat, as the clamps would have to close on too large adiameter of stuffed product, breaking and bursting the film due to thefriction and sudden increase in pressure caused by the displacement ofthe large amount of meat to be separated.

As a result of the slow stuffing in both the manual and the mechanicaloperation the system productivity is low. This is made worse by the needfor frequent stoppages to replace the tube containing the shirred orcompressed net due to the limited amount of net that can be loaded onthe tube. The piece piercing operation and their manipulation to subjectthem to a vacuum in order to remove the air simply adds manpower cost tothe operation, which in the case of the most automated operation canrepresent up to a 60% addition to the rest of the operation.

Because of the low accuracy of the manual operation, when this is thecase the weight control is poor. When a more or less viscous productmade of meat parts is pumped through a large-diameter tube thepossibility that one or several meat parts on the open end of the tubefall in the preceding piece introduces an element of weight variationeven when the meat corresponding to each piece is independently pushedand controlled by the stuffing machine.

Oscillation in the size of the pieces in the case of the manual systemare inherent to the process, while in the case of the mechanical systemthey are due to the difference in the net traction depending on whetherthe net tube has just been placed or it is about to run out of net. Thisdifference is due to the different contact area in either case betweenthe net and the tube and is made worse by the high tension to which thenet is subjected as a result of the tube diameter.

Other oscillations are produced when loading the nets on the pneumaticloaders, when it is frequent for net portions loaded afterwards to beinserted under the previously loaded net. As the net loaded at the endis the first to be dispensed during the application, the aforementionedcovered fragments will be released with greater difficulty, giving riseto short and tightened pieces with a risk of no overlapping and losingmeat, or to soft and long pieces when the covered fragments are suddenlyreleased.

Both the films and the elastic nets used to wrap meat products areexpensive and constitute an important part of the production cost.Current production systems, whether manual or mechanical, are notoptimised as regards using the necessary amount of these materials. Inthe manual operation case, the waste of material is due t theoscillation in the length of the pieces, often inevitably using morematerial than is required, as described above, as well as to the excessmaterial wasted on the ends to hold the pieces as they are tightened toprovide the necessary tension and clip or staple them. In the case ofautomatic machines, the latter aspect is controlled better as the lengthof the ends is controlled by the distance between the separating clamps,although this distance is greater than is necessary and is imposed bythe size of the clamps.

The air trapped during the stuffing constitutes one of the most seriousdrawbacks of these systems. Air trapped in the stuffing is locatedbetween the film and the surface of the meat, and given the filmcharacteristics, is not eliminated during cooking. This results infaults of the surface appearance of the products when they are releasedfrom the net for their final packaging. This is especially problematicin this type of products, which are expensive and of high quality. Theareas in which the air is located are paler in colour than the rest whenthe products have been smoked, they are recessed and when collagen filmsare used these have adherence problems. Products affected by thisproblem must be declassified and sold at a lower price or reprocessed.

The trapped air is incorporated in the product during the stuffing dueto the low pressure in which these types of products are stuffed. Theair may reach the interior of the wrapping through the space between thefilm and the stuffing tube. The greater the tube diameter, the greaterthe perimeter through which the air can enter, and the lower thepressure exerted by t product on the outside opposing the entry of air.In the case of products stuffed with a piston, the stuffing operationpushes all the air in the tube in which the product must be pushed intothe film and net assembly, thereby worsening the problem.

To minimise the impact of this problem, he stuffed products are piercedso that air is allowed to escape during the heat process, or previouslyperforated films are used. In the first case this represents anadditional operation that reduces the productivity of the process andthat does not solve the problem fully, while the second case may weakenthe film, as well as increasing its price.

Another common problem is loss of overlapping. The mechanical problemsof the process mean that the overlapping of the longitudinal film endsis frequently lost. When this occurs, the product is not correctlycovered by the film, so that meat is lost and problems of many kindsarise, mainly of appearance and adherence to the net, which cannot belater removed without tearing, resulting in poor quality products.

DESCRIPTION OF THE INVENTION

The method and complementary device disclosed by the invention solve theaforementioned drawbacks in a fully satisfactory manner. For thispurpose, its essential characteristic is that unlike the cited methodsthan make the meat pass through large-diameter tubes near the productbeing stuffed, the tube through which the meat mass is inserted has asmall diameter independent of the size of the finished product. The filmconstituting the inner wrapping, after being shaped from a coil as acylinder with its longitudinal edges overlapping, is tightly adapted tothe small diameter forming for this purpose longitudinal wrinkles orfolds uniformly distributed along its circumference. The elastic netthat constitutes the outer wrapping, which for an applicationsimultaneous with that of the film has been previously shirred in anexternal tube concentric to the meat tube, melds with the film on thefinal part of the latter, externally holding the film and runningtogether with it without being subjected to any significant elasticradial elongation, until after passing through a retaining system thatprevents the return of the meat product the double casing is filled bythe meat mass that is pushed by the portioning stuffing machine,increasing its diameter while the longitudinal folds unfold and the nettightens until the product reaches the suitable diameter and it isclosed by a double staple or clip. As these operations are carried out,the packaged product is evacuated by a conveyor belt placed at theoutlet of the stapler or clipping machine while exerting a uniformtraction on the double casing until it is dispensed in a controlledfashion. Individual pieces can be separated at the end of the evacuationbelt cutting the double casing between the two clips either manually orwith an automatic cutting system.

This difference in the diameter of the tube through which the meat isstuffed allows on one hand allows adapting the system to a conventionalstuffing-portioning machine and to an also conventional fast doubleclipper, synchronised for automated operation whose advantages areexplained in greater detail hereinafter, and on the other hand the useof net loading tubes with a considerably smaller diameter able to load asubstantially greater amount of net by its multilayer shirring thatminimises friction and allows a correct unshirring, increasing theautonomy of the system.

In the traditional system the meat is introduced in the double casing,first opening the latter in the form of a pouch to allow the meat topass. In the system disclosed, it is the meat that makes its way intothe casing with the pressure provided by the pumping system of thestuffing machine. This prevents the entry of air from the outside andaccess on the inside as the tube is always full of meat. In addition,this system facilitates maintaining the overlapping of the film edgesthroughout the process as it is not extended to its full diameter untilits exit from the stuffing tube when it is already protected by theexternal net.

The method object of the invention is reduced to practice by adding, toa conventional stuffing-portioning machine and a conventional doubleclipping machine synchronised for automatic operation, a device able toshape into a cylinder a film intended to wrap food products, supplied inthe form of a coil, a stuffing tube with a diameter that is considerablysmaller than that of the finished product and adaptable to the doublefast clipper, a tube with a diameter slightly larger than that of thestuffing tube and concentric to it, meant to contain the suitablyshirred net, allowing the film to pass between the tubes, a frame ableto support the aforementioned elements to each other, a retaining systemto prevent the meat product from returning after it leaves the stuffingtube and a traction and evacuation system for the wrapped products.

This assembly forms a system that can continuously and automaticallyprovide individual pieces with a controlled volume stuffed in a doublecasing with a film and a net separated by a double clip or staple. Theuse of a small diameter stuffing tube allows its adaptation to a fastdouble clipper and its synchronisation with a stuffing-portioningmachine. The system admits several diameters of the stuffing tube andthe tube containing the net, the film always running between the two,suitably shirred in a longitudinal sense. The smaller the tube diameterthe greater the amount of shirred net it can contain, so that thefrequency of the stoppage times to restore it is reduced.

When elastic nets are used the pressure transmitted to the inside of thefilm and net assembly, unlike when a rigid packaging is used, means thatthe packaging material can swell to the required diameter. This allowscontrolling the size of the pieces according to the amount of doubleelastic casing supplied to each one. If the amount of double elasticcasing is greater or lesser, longer or shorter pieces will respectivelybe obtained, with a higher or lower net tension on the meat product.

This amount can be supplied manually, pulling on the double casingduring stuffing, or automatically, such as using a conveyor belt with acontrolled speed that removes the stuffed products while applyingtraction on the double casing being stuffed.

DESCRIPTION OF THE DRAWINGS

To complement the description being made and in order to aid a betterunderstanding of the characteristics of the invention, according to anexample of a preferred embodiment, this description is accompanied by aset of drawings forming an integral part of it where for purposes ofillustration and in a non-limiting sense the following is shown:

FIG. 1 shows, according to a schematic representation in a sideelevation view, a stuffing installation made according to the object ofthe invention where an adjustable speed conveyor has been added at theoutlet of double fast.

FIG. 2 shows, according to the schematic representation in perspective,a detail of certain elements embodying the method of the invention.

FIG. 3 shows an enlarged detail of FIG. 1, schematically showing theinternal operation of the separation and clipping system in twosituations. Specifically, situation A shows the system at the time ofstuffing and situation B at the time of clipping.

FIG. 4 shows the arrangement of the separation clamps of the fastclipping machine in the stuffing position (A) and in the separationpositions (B and C).

FIG. 5 shows a sectional view of a detail of the space between the nettubes and the meat, in which the longitudinal folds of the inner filmand its overlap area can be seen.

FIG. 6 shows a perspective schematic representation of the elementsrequired in the successive stages of the multilayer net shirringaccording to the invention.

FIG. 7 shows how a conventional net shirring device can be used with theadditional use of a transfer tube to shirr the multilayer net on areduced diameter tube.

PREFERRED EMBODIMENT OF THE INVENTION

In view of the described figures, provided solely for purposes ofillustrating the invention, the scope of which includes otherarrangements or designs of the set of components that configure thesystem and of the individual components, it can be seen that the objectof the invention is an automatic method and device for a full stuffingof meat products without air in a film and net that solves the drawbacksof currently used systems, none of which obtains production rates aboveseven pieces per minute, managing a spectacular improvement in theproduction rate while saving manpower, double casing, and increasing thequality of the finished products eliminating the trapped air andobtaining an optimum uniformity of shape and weight.

For a better understanding of the system, its component elements andtheir operation are now described.

A portioning stuffing machine (1) (FIG. 1); this is a commonly usedmachine in meat industries, and basically consists of a pump that canpush and stuff meat mass in the suitable casing either continuously ordiscontinuously. An automat controls both the impulsion flow rate andthe volume impelled each time, thus acting as a dosifier. The machine isprovided with a hopper for feeding the meat mass. A vacuum can beapplied to both the hopper and the pump body.

An applicator device for the film and elastic net (FIG. 2). Providedwith the same elements as conventional applicators, with the differencethat the tube (4) trough which the meat is pushed has a considerablysmaller diameter than that used in conventional applicators. Thisdiameter is enough to allow the meat pushed by the stuffing-portioningmachine to pass. The first beneficial result of the use of this reduceddiameter tube is that the diameter of the tube of the net (8) can becorrespondingly reduced and its net loading capacity correspondinglyincreased.

In order for the recently formed film cylinder to pass with its sideedges overlapping through the space between the meat tube and the net,it must form evenly spaced longitudinal folds (7) that remain until theend of the meat tube, as shown in FIG. 5.

The second beneficial consequence of the meat tube with a reduceddiameter is that it can be connected to a fast automatic clippingmachine prepared for clipping meat pieces in casings with a medium andsmall diameter, that is common in the meat industries. This allowsquickly filling and stapling meat products with a large diameter in adouble film and net casing making use of the expansion capacity of thedouble casing due to the longitudinal folds formed in the film and tothe transverse elasticity of the net. This double clipper can besynchronised with the stuffing machine (1) such that when the latter haspushed the programmed amount of meat into the double casing, it stopsfor a moment to allow the double clipper to suitably staple the recentlystuffed piece, immediately repeating the process.

The third positive consequence of the meat tube with a reduced diameteris that it obtains air-free pieces by an intermittent pumping of themeat mass. This allows the tube to be full of meat at all times,preventing air from entering it. In addition, a meat retaining system(11) can be disposed that acts as a barrier to the external air andprevents the meat from moving backwards between the film and the tube,preventing film adherences, dirt and increased resistance to the freeflow of the film. Applying this system to large diameter tubes isdifficult as the greater perimeter increases friction excessively.

A final beneficial consequence of the reduced diameter stuffing tube isthat it simplifies the separation of the pieces from each other so thatthey all have the same volume and thus the same weight. The greater thetube diameter the greater the variation in the weight of the pieces asit is more likely that a meat part in the separation area falls in onepiece or the other at the time of separation. If the tube is small thispart is held more firmly and it can more easily be cut by the clamps.

A fast automatic double clipping machine (2). Closes the casingcontaining the meat product by a simultaneous application of twostaples, one at the end of the piece that has just been stuffed andanother at the start of the following piece, separated by the minimumspace required to allow their application and ensure the closure. Themachine also separates one piece from another by a pair of doubleseparation clamps (19) and (20), FIGS. 3 and 4, which strangle theproduct on the area where it is to be stapled and then separate by thenecessary space to allow applying the staples. These machinesincorporate a tube through which the meat is made to pass and that isconnected to the stuffing machine. In the system of the invention thistube is the reduced diameter tube (4) described previously in the filmand elastic net applicator.

A uniform traction and evacuation system. A uniform traction andevacuation is achieved by a conveyor belt (12) placed at the outlet ofthe clipping machine that receives the pieces uncut and carries them ata controlled speed as they are stuffed. This speed can be constant orintermittent, this is, advancing during the stuffing and stopping whenthe staple is applied. This facilitates regulating the size of thepieces. In the case of elastic casings size cannot be satisfactorilyregulated by a brake or a piece length limiter, as two variables controlit, length and diameter, instead of one, length, as in the case of rigidcasings. As the object of the system is to stuff pieces with a constantweight and/or volume, the simplest way to ensure pieces of uniform sizeis to provide each piece with exactly the same amount of double elasticcasing. This is achieved by a conveyor belt placed at the outlet of theclipping machine that removes stuffed products at the same speed as thedouble casing is supplied. The weight of the products ensures thefriction needed to prevent slippage, so that the double casing is pulledat a constant speed as the product is stuffed.

One of the great advantages of the system derived of the reduceddiameter of the stuffing tube as explained above is that support tubescan be employed for the shirred net whose diameter is also smaller, sothat they can contain a much greater amount of net without subjecting itto a high radial tension, also achieving a smoother unshirring due tothe lower friction with the tube. Below is explained how the net isshirred in multiple layers on reduced diameter tubes.

The multilayer shirring of the net of the invention, FIG. 6, is obtainedin a simple manner by the same shirring system of the conventionalsystem using an additional tube (27) that, far from complicating thesystem simplifies it. The first operations are performed similarly tothe conventional system, with the only difference that instead of takingplace on the final tube of the net (8), which in this case has a smallerdiameter, take place on a transfer tube (27), with a diameter similar tothe net tube of the conventional system and a lower end having an areaof a few centimetres in the shape of a truncated cone (28) to facilitatetransferring the net to the definitive net tube, as will be explainedbelow. After the transfer tube has been suitably threaded with the net(29) and the latter has been trapped in the teeth of the loader, thedefinitive net tube (8) is placed inside the transfer tube and the net(30) will begin to be pushed towards the bottom end of the net tube,which remains hidden inside the transfer tube showing only the base sothat it is held to the stuffing machine, also acting as a bottom stopfor the net. When the net reaches the bottom end of the transfer tube itis accumulated in the truncated cone shaped area, such that as soon asthe downward pressure ends because the loader begins its upward run thenet, due to the special shape of the tube end, falls spontaneously onthe net tube. As these operations are successively repeated the innernet tube is orderly loaded with the net (31) and (9) that occupies theentire space included between the lower tube and an imaginary coaxialtube external to the one with a diameter similar to that of the transfertube. As the inner tube is loaded the transfer tube rises resting on theloaded net, so that all individual loading operations have the same runand load the same amount of net, equivalent to the length of thetransfer tube, unlike the traditional method in which as the net isloaded the shirred net is less, thus not allowing to use the entirelength of the support tube.

FIG. 7 shows how the previously described method relating to the manualshirring method can be applied using the same additional elements, thisis, a transfer tube (27), on the conventional net shirring mechanicalprocess, where the net tube (8) is placed on a platform (32) which isalternatively moved up and down by a pneumatic piston (33). The netloader (24) is fixed in this case but its relative motion with respectto the tube and the net is the same as in the manual loading. In thiscase the transfer tube (27) has an internal guide (34) that is insertedin the net tube to provide rigidity to the system. This inner guide mayalso be used for manual shirring.

System Operation.

The system of the invention is started after the stuffing machine beginsto push the meat through the tube (4), pushing the closed double casingforward. The meat thus fills the portion of double casing supplied,which expands as the longitudinal folds become unshirred and thetransverse elastic rings of the net are fully tightened. After the meatcorresponding to the piece has been stuffed the stuffing machineautomatically interrupts the pumping and the clamps (19) and (20) of theclipping machine close, strangling the double casing and the meat, thenopening to displace the meat contained in the space intended for thedouble staple. At this time the die (21) and the matrix (22) of thedouble clipper close on the strangled portion of double casing withoutmeat, placing a pair of staples as seen in FIG. 3B. the clampsimmediately open and come together as the matrix and die separate toreach the new stuffing position FIG. 3A and the stuffing of the newpiece begins. After the first piece has been produced, it is depositedon the conveyor belt so that the belt can pull on the piece to form thesecond and subsequent pieces. Stuffing of the successive pieces isautomatically performed in this manner until the stock of shirred net orfilm in the coil is exhausted and it is necessary to reload them,restarting the process.

EXAMPLES

The following examples are provided to determine the scope andcharacteristics of the invention, which are not meant to limit theinvention and are included only for purposes of explanation.

They describe the characteristics and parameters of the production ofmeat products in film and net according to various traditional systems,comparing them in each case to the production of various finishedproducts using the system disclosed in the invention. The most importantpoints to consider in the comparison are the following:

-   -   Manpower used    -   Width and length of the double casing used per piece.    -   Amount of net loaded per operation    -   No of pieces stuffed for each net load    -   Production rate    -   % of pieces with surface air pockets in the finished product.

EXAMPLE 1 Traditional System Disclosed System Equipment Marlen OPTIHandtmann VF 200 140 (4000 Kg/hora) Marlen COV Poly Clip FCA Portioner3462 Tipper Tie Disclosed system TCM with 50 mm tube 2250 Pumpable FilmCoffi Coffi 380 mm 380 mm coil coil 100 m 100 m Net 16/5 20 metre 16/543 metre polyester loads polyester loads Diameter of the 100 mm 50 mmmeat tube Diameter of the 120 mm 62 mm net tube Weight of the 1750 g1750 g pieces produced Length of the 250 mm 220 mm pieces producedDiameter of the 104 mm 110 mm pieces produced Length of the 2 × 30 mm 2× 20 mm loose ends after the clips Length of casing 370 mm 320 mm usedper piece N° of stuffed 54  134 pieces per net load Persons used 1.5operators 1 operator Rate in pieces per 6 pieces/ 22 pieces/minuteminute minute % finished pieces 2% 0% with air

EXAMPLE 2 Traditional System Disclosed System Equipment Manual HandtmannVF 200 Applicator (4000 Kg/hour) GAROS H 120 Poly Clip FCA 3462Disclosed system with 50 mm tube Film Coffi Coffi 470 mm 440 mm 100 m100 m Net 20/3 15 m 20/3 35 m polyester loads loads Diameter of the 120mm 50 mm meat tube Diameter of the 142 mm 62 mm net tube Weight of the2200 g 2200 g pieces produced Length of the 250 mm 250 mm piecesproduced Diameter of the 120 mm 120 mm pieces produced Length of the 2 ×80 mm 2 × 20 mm loose ends after the clips Length of casing 460 mm 350mm used per piece N° of stuffed 32 100 pieces per net load Persons used2 operators 1 operator Rate in pieces 4 pieces/minute 18 pieces/minuteper minute % finished 1% 0% pieces with air

EXAMPLE 3 Traditional system Disclosed system Equipment Marlen OPTIHandtmann VF 200 140 (4000 Kg/hora) Marlen COV Poly Clip FCA 3462Portioner Tipper Tie Disclosed system TCM 2250 with 50 mm tube PumpableFilm Coffi Coffi 570 mm 570 mm coil coil 100 m 100 m Net 22/3 20 m 22/335 m polyester loads polyester loads Diameter of the 120 mm 50 mm meattube Diameter of the 142 mm 62 mm net tube Weight of the 4500 g 4500 gpieces produced Length of the 340 mm 310 mm pieces produced Diameter ofthe 144 mm 150 mm pieces produced Length of the 2 × 30 mm 2 × 20 mmloose ends after the clips Length of 490 mm 420 mm casing used per pieceN° of stuffed  40 83 pieces per net load Persons used 1.5 operators 1operators Rate in pieces 6 pieces/ 11 pieces/minute per minute minute %finished 2% 0% pieces with air

EXAMPLE 4 Traditional system Disclosed system Equipment Marlen OPTIHandtmann VF 200 140 (4000 Kg/hora) Marlen COV Poly Clip FCA 3462Portioner Brechteen Disclosed system 2210 C 5″ with 50 mm tube FilmCoffi Coffi 620 mm 570 mm coil coil 100 m 100 m Net 22/3 15 m 22/3 35 mpolyester loads polyester loads Diameter of the 120 mm 50 mmm meat tubeDiameter of the 142 mm 62 mm net tube Weight of the 4500 g 4500 g piecesproduced Length of the 310 mm 310 mm pieces produced Diameter of the 150mm 150 mm pieces produced Length of the 2 × 80 mm 2 × 20 mm loose endsafter the clips Length of casing 540 mm 420 mm used per piece N° ofstuffed  27 83 pieces per net load Persons used 2 operators 1 operatorRate in pieces 5 pieces per 11 pieces/minute per minute minute %finished 1% 0% pieces with air

In view of the above examples, the advantages of the system disclosed inthe invention over traditional systems in these specific cases are clearand can be summarised as follows:

-   -   Double casing saving: between 13 and 24%.    -   Reduction of the number of operators needed: between 33 and 50%.    -   Increase in the working rate: between 220 and 450%    -   Increase in the number of parts stuffed for each net load:        between 207 and 312%.    -   Reduction of parts with trapped surface air: 100%.

Below are shown comparative data on the examples made with thetraditional procedure and with the procedure of the invention, showingthe difference between the diameters of the meat stuffing tube and thefinal product on one hand, and of the net tube and the final product onthe other, showing that in the system of the invention the difference indiameters is considerably greater than in the traditional procedure.

Final prod. Meat tube Net tube diameter diameter Difference diameterDifference (1) (2) (1 − 2) (3) (1 − 3) Traditional system, patentexamples (Values in mm) 104 100 4 120 −16 120 120 0 142 −22 144 120 24142 2 150 120 30 142 8 Disclosed system, patent example (Values in mm)110 50 20 62 48 120 50 70 62 58 150 50 100 62 88 150 50 100 62 88

1. A method for producing meat products having a final diameter, bystuffing meat mass in a double casing comprising a film and a net, themethod comprising the steps of: inserting meat mass into a cylinderformed by the film and surrounded by the net, using a stuffing tube forinserting the meat mass into the cylinder, the stuffing tube (4) havinga diameter that is smaller than the final diameter of a meat product;and shaping the film (5) into the cylinder for receiving said meat massthrough said stuffing tube (4), said step of shaping the cylindercomprising the step of forming longitudinal folds (7), wherein thediameter of the cylinder is adapted to the diameter of the stuffing tube(4) while allowing for radial expansion of the cylinder when saidcylinder is fed with meat mass through said stuffing tube (4), byunfolding the folds (7).
 2. A method according to claim 1, wherein thefilm is longitudinally shirred on the stuffing tube.
 3. A methodaccording to claim 1, wherein the meat product makes its way inside thedouble film and net casing, radially expanding until reaching the finaldiameter.
 4. A method according to claim 1, wherein the net is shirredin a multilayer arrangement on a tube whose diameter differs from thatof the finished product by more than 18 mm.
 5. A method according toclaim 1, wherein the film and the net do not reach their full radialexpansion until the meat product is inside the double casing.
 6. Amethod according to claim 1, including preventing air from entering themeat product.
 7. A method according to claim 1, including preventing themeat product from returning by a retaining system placed at an outlet ofthe stuffing tube.
 8. A method according to claim 1, including providingan automatic product traction and evacuation system for controlling theproduct size.
 9. A method according to claim 1, including automaticseparating and clipping or stapling operations that begin before themeat product reaches its final diameter.
 10. A method according to claim1, wherein said stuffing tube has a diameter that is more than 40 mmsmaller than the final diameter of the meat product.
 11. A methodaccording to claim 1, wherein the longitudinal folds (7) are formeduniformly distributed along the circumference of the cylinder.
 12. Amethod according to claim 1, wherein the film is shaped into a cylinderwith longitudinal edges of the film overlapping.
 13. A method accordingto claim 1, wherein the film is shaped from a coil.